I started out using a pick and played that way for over 20 years. In 2002, I was presented with the opportunity to join a touring blues band. I met with the BL (Guitarist, Lead Singer) on a Friday night. He gave me a cd, told me to pick two songs and be ready for the audition on Monday. I had read that many blues guitarists prefer their bass players to use finger style so I spent the weekend learning the entire cd in finger style and got the gig. I have used finger style ever since and rarely use a pick. I find that I am faster, more accurate, and it make muting easier. I also like the tone better.

I sometimes regret it because some of the songs I play could really benefit from the different sound but I just don't like it.

I have small hands and play the bass very... diagonal, with the body tilted downward and the neck tilted upward so my fretting hand is comfortable, however in this position I find it hard to play with a pick.

I use both. I would like to slap but it triggers my tendinitis. I'll use whatever suits me including hitting the strings with manicotti dipped in epoxy and fairy dust. I eschew all notions of there being one way or one best way to do anything except for the one universal truth that the bitter comes out better on a stolen guitar.
Mugre

I play with fingers mostly and use a thumb pick on one tune that has a descending scale run in the middle break that is too fast for my fingers. One day I'm going to master that run and leave the thumb pick at home!